Moisture sensor with capacitive moisture measuring element and method of determining air humidity

ABSTRACT

In a method of determining air humidity, a corrected moisture signal is calculated for a moisture signal (Hi) ascertained from electrical properties of a capacitive moisture measuring element. In a measuring phase ( 30 ) with rising relative air humidity (RH), the corrected moisture signal is the current moisture signal (Hi) increased by a correction value, whereas in a measuring phase ( 31 ) with falling relative air humidity (RH) the corrected moisture signal is the current moisture signal (Hi) reduced by a correction value. Depending on the respective properties of the moisture measuring element and the required degree of measuring accuracy, the correction value is constant or is taken into consideration in dependence on the relative air humidity RH. This method provides a higher level of measuring accuracy with a moisture sensor equipped with the moisture measuring element.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a method of determining moisture with a capacitive moisture-sensitive element, and an apparatus for carrying out the method.

[0003] 2. Description of Prior Art

[0004] Such apparatuses and methods are advantageously used in the heating, ventilation and air-conditioning art (HVAC) for buildings for determining the air humidity in a room or in a device for supplying or discharging air.

[0005] Capacitive moisture measuring elements deliver a capacitance value in dependence on the air humidity in the area around the measuring element. That capacitance value can be measured by means of an electronic evaluation system. A current moisture value is ascertained with the measured capacitance value, using further parameters such as temperature and comparative parameters.

[0006] Capacitive moisture measuring elements are available on the market in various different forms, and by way of example reference will be made here to ‘HS11100’ from Humirel, ‘MiniCap2’ from Panametrics, ‘H5000’ from Gefran, ‘Hygromer C-94’ from Rotronic and ‘HC1000’ from E+E Elektronik. The manufacturers of moisture measuring elements generally also propose circuits, by means of which air humidity can be measured. In many cases an oscillator circuit with a generally known multivibrator ‘555’ is proposed for use of the specified moisture measuring elements.

[0007] U.S. Pat. No. 5,844,138 also discloses a device of that kind in which a capacitive moisture sensor is part of an oscillator. The frequency of the oscillator is dependent on the condition of the moisture sensor and thus the moisture level.

[0008] In known devices for measuring air humidity, the capacitive moisture sensor used is considered as an ideal capacitor involving a variable capacitance. Experience has shown that this simplification, for certain uses, gives rise to unacceptably large deviations between an air humidity value ascertained in the known manner and the air humidity value which is actually present. In particular mention should be made of the fact that the properties of individual examples in the case of capacitive moisture measuring elements of the same kind can suffer from relatively severe scatter.

BRIEF SUMMARY OF THE INVENTION

[0009] The object of the present invention is to improve known methods of determining air humidity in such a way that it is possible to achieve a substantial improvement in the level of measuring accuracy with a conventional capacitive moisture measuring element. In this respect the invention also seeks to provide an apparatus with which the method can be carried into effect.

[0010] In accordance with a first aspect of the present invention, there is provided a method of determining air humidity with a capacitive moisture measuring element, comprising:

[0011] a method step in which a current moisture signal is ascertained from electrical properties of the moisture measuring element, and

[0012] a method step in which a corrected moisture signal is calculated from the current moisture signal, wherein in a measuring phase with rising relative air humidity RH the corrected moisture signal is the current moisture signal increased by a correction value a(RH) and wherein in a measuring phase with falling relative air humidity RH the corrected moisture signal is the current moisture signal reduced by a correction value a(RH).

[0013] In accordance with a second aspect of the present invention, there is provided a moisture sensor comprising a ca According to one embodiment, a clip is provided that engages with the water water hole portion and the insert so as to fix the insert to the cylinder block.

[0014] According to one embodiment, the cylinder block includes a groove formed in the water hole portion of the upper deck, and the insert has a key formed therein and fitted in the groove so as to fix the insert to the cylinder block.

[0015] A cooling apparatus of an internal combustion engine according to another aspect of the invention includes a closed deck-type cylinder block and an insert, wherein the closed deck-type cylinder block has a water jacket for causing engine cooling water to flow therein to cool the engine and a water jacket wall surrounding the water jacket, and an upper deck including a water hole formed therein for causing the cooling water to flow therethrough. The insert is disposed in the water jacket and is inserted into the water jacket through the water hole. A stopper for preventing the insert from moving downstream in a flow direction of the cooling water is formed to the water jacket wall, and the insert engages the stopper such that the insert is fixed in position in the flow direction of the cooling water.

[0016] According to one embodiment, the stopper is a protrusion formed in at least one of a bottom wall portion and an outer side wall portion of the water jacket wall.

[0017] According to one embodiment, the stopper is an extension extending from a cylinder head mounted to the cylinder block into the water jacket.

[0018] According to one embodiment, the stopper is an extension extending from a cylinder head gasket mounted to the cylinder block into the water jacket.

[0019] According to one embodiment, the stopper is a protrusion protruding from a tight plug mounted to the cylinder block into the water jacket.

[0020] According to one embodiment, the stopper is a chaplet used in the manufacture of the cylinder block, and which remains in the water jacket.

[0021] A cooling apparatus of an internal combustion engine according to one aspect of the invention includes a closed deck-type cylinder block and an insert, wherein the closed deck-type cylinder block has a water jacket for causing engine cooling water to flow therein to cool the engine, and an upper deck including a water hole formed therein for causing the cooling water to flow therethrough. The insert is disposed in the water jacket and is inserted into the water jacket through the water hole. The insert includes an upstream portion having a streamline configuration.

[0022] By fixing the insert relative to the cylinder block at the water hole portion, the insert is prevented from being dislocated from its normal position when receiving a pressure from the cooling water, while feasibility of mounting the insert into the water jacket is maintained.

[0023] By causing the insert to contact the stopper formed to the water jacket wall, the insert is prevented from being dislocated from its normal position when receiving a pressure from the cooling water, while feasibility of mounting the insert into the water jacket is maintained.

[0024] By forming the insert to have an upstream portion having a streamline configuration, the pressure acting on the insert from the cooling water is minimized. As a result, the insert is prevented from being dislocated from its normal position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other objects, features, and advantages of the present invention will become apparent and will be more readily appreciated from the following detailed description of preferred exemplary embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0026]FIG. 1A is a plan view of a cylinder block to which a cooling apparatus of an internal combustion engine according to a first embodiment of the present invention is applied;

[0027]FIG. 1B is a transverse cross-sectional view of the cooling apparatus of an internal combustion engine according to the first embodiment of the present invention;

[0028]FIG. 1C is a plan view of the cooling apparatus of an internal combustion engine according to the first embodiment of the present invention;

[0029]FIG. 1D is a longitudinal cross-sectional view of the cooling apparatus of an internal combustion engine according to the first embodiment of the present invention;

[0030]FIG. 2A is a cross-sectional view of a cooling apparatus using a wedge of an internal combustion engine according to a second embodiment of the present invention;

[0031]FIG. 2B is a cross-sectional view of a cooling apparatus using a rubber of an internal combustion engine according to the second embodiment of the present invention;

[0032]FIG. 3A is a plan view of a cooling apparatus of an internal combustion engine according to a third embodiment of the present invention;

[0033]FIG. 3B is a cross-sectional view of the cooling apparatus of an internal combustion engine according to the third embodiment of the present invention;

[0034]FIG. 4A is a plan view of a cooling apparatus of an internal combustion engine according to a fourth embodiment of the present invention;

[0035]FIG. 4B is a cross-sectional view of the cooling apparatus of an internal combustion engine according to the fourth embodiment of the present invention;

[0036]FIG. 5A is a plan view of a cooling apparatus of an internal combustion engine according to a fifth embodiment of the present invention;

[0037]FIG. 5B is a cross-sectional view of the cooling apparatus of an internal combustion engine according to the fifth embodiment of the present invention;

[0038]FIG. 5C is a plan view of a cooling apparatus of an internal combustion engine according to a variation of the fifth embodiment of the present invention;

[0039]FIG. 6 is a cross-sectional view of a cooling apparatus of an internal combustion engine according to a sixth embodiment of the present invention;

[0040]FIG. 7A is a cross-sectional view of a cooling apparatus of an internal combustion engine according to a seventh embodiment of the present invention;

[0041]FIG. 7B is a perspective view of a stopper portion of the cooling apparatus of a internal combustion engine according to the seventh embodiment of the present invention;

[0042]FIG. 8A is a transverse cross-sectional view of a cooling apparatus of an internal combustion engine according to an eighth embodiment of the present invention;

[0043]FIG. 8B is a longitudinal cross-sectional view of the cooling apparatus of an internal combustion engine according to the eighth embodiment of the present invention;

[0044]FIG. 8C is a perspective view of a tight plug of the cooling apparatus of an internal combustion engine according to the eighth embodiment of the present invention;

[0045]FIG. 9A is a transverse cross-sectional view of a cooling apparatus of an internal combustion engine according to a ninth embodiment of the present invention;

[0046]FIG. 9B is a longitudinal cross-sectional view of the cooling apparatus of an internal combustion engine according to the ninth embodiment of the present invention;

[0047]FIG. 10A is a longitudinal cross-sectional view of a cooling apparatus of an internal combustion engine according to a tenth embodiment of the present invention; and

[0048]FIG. 10B is a plan view of the cooling apparatus of an internal combustion engine according to the tenth embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0049] A cooling apparatus of an internal combustion engine according to the present invention will be explained with reference to FIGS. 1A-10B. FIGS. 1-10 illustrate an apparatus according to first—tenth embodiments of the present invention, respectively.

[0050] Portions having the same or similar structures over the first through tenth embodiments of the present invention are denoted with the same reference numerals over the first through tenth embodiments of the present invention.

[0051] First, the portions having the same or similar structures over the first through tenth of the present invention will be explained with reference to FIGS. 1A-1D.

[0052] A cooling apparatus of an internal combustion engine according to the present invention includes a cylinder block 10 and an insert 1. The cylinder block 10 is a closed deck-type cylinder block. The cylinder block 10 has a water jacket 11 continuously extending around cylinder bores 13 and a cylinder bore wall 14. The cylinder block 10 has 10 a and a plurality of water holes 12 formed in the upper deck 10 a. The upper deck 10 a includes a water hole portion 10 b surrounding the water hole 12. The water holes 12 are formed discontinuous in the extending direction of the water jacket 11. The water hole 12 is a hole through which engine cooling water flows from the water jacket 11 of the cylinder block 10 to a water jacket of a cylinder head. The water hole 12 communicates with the water jacket 11.

[0053] The insert 1 is disposed in the water jacket 11 and is inserted through the water hole 12 into the water jacket 11. The cylinder bore wall 14 has a portion downwardly distanced from a combustion chamber, which should be prevented from being over-cooled. The insert 1 is disposed close to that portion to be prevented from over-cooling, of the cylinder bore wall 14 such that the insert 1 contacts or is slightly spaced from an outer surface of that portion. The insert 1 minimizes the flow and amount of the cooling water between the insert 1 and that portion of the cylinder bore wall 14 so that that portion of the cylinder wall 14 is not over-cooled.

[0054] When the insert 1 is inserted into the water jacket 11 through the water hole 12, a transverse cross section of the insert 1 has to be smaller than a size of the water hole 12, while after the insert 1 has been inserted in the water jacket 11, the insert 1 preferably expands to be larger in size. Due to the deformation, a clearance between the insert 1 and the cylinder bore wall 14 is decreased, or the insert 1 is brought into contact with the cylinder bore wall 14. As a result, the cooling water is prevented from flowing much between the insert 1 and the cylinder bore wall 14, so that the cylinder bore wall 14 is prevented from being over-cooled.

[0055] If the insert 1 is moved and dislocated from a normal position (a position where the insert 1 contacts or is close to the cylinder bore wall 14) when receiving a flow pressure from the cooling water, the effect of preventing the cylinder bore wall 14 from being over-cooled will be decreased and in some cases the water hole 12 may be blocked. Therefore, the insert 1 should be fixed in position relative to the cylinder block 10 by a proper fixing or support structure so that the insert 1 is stably held to the normal position.

[0056] The fixing and supporting structure 30 can take various structures according to respective embodiments of the present invention.

[0057] Next, structures unique to each embodiment of the present invention and the effects thereof will be explained below.

[0058] In the first embodiment of the present invention, as illustrated in FIG. 1, the insert 1 includes a support 2 and an elastic member 3 fixed to the support 2. The elastic member 3 has a feature of expanding in size after the insert 1 has been inserted in the water jacket 11, so that a surface of the elastic member 3 opposing the cylinder bore wall 14 contacts or moves close to the cylinder bore wall 14. The elastic member 3 may be constructed of, for example, a rubber foam which contains a binder and is compressed, so that the rubber foam has a feature of expanding when it contacts water (or LLC, long life coolant). When the water jacket is filled with water or LLC at the stage of engine assembly or vehicle assembly, the size A (smaller than the size of the water hole) at the stage of insertion of the insert 1 changes to the size B (greater than the size of the water hole) at the stage after expansion of the elastic member 3. FIGS. 1B and 1C show that the elastic member 3 contacts the cylinder bore wall 14.

[0059] The insert 1 is demountably supported by the cylinder block 10 via the support 2 due to the elasticity of an upper arm 2 a and a lower arm 2 b. More particularly, the support 2 is fixed relative to the water hole portion 10 b surrounding the water hole 12 due to the structure that the upper arm 2 a elastically contacts the water hole portion 10 b, and is fixed relative to a protrusion 15 formed in the bottom wall of the water jacket due to the structure that the lower arm 2 b elastically contacts the protrusion 15. By this structure, the insert 1 is fixed in position even when a flow pressure acts on the insert I from the cooling water. The insert 1 is held by the water hole portion 10 b and the protrusion 15 so as not to be dislocated from the normal position. The upper arm 2 a and the lower arm 2 b of the support 2 constructs the fixing and supporting structure 30 of the first embodiment of the present invention.

[0060] With an effect of the first embodiment of the present invention, since the upper arm 2 a and the lower arm 2 b of the support 2 have an elasticity, the upper arm 2 a and the lower arm 2 b of the support 2 can be elastically deformed and shrunk, so that the upper arm 2 a and the lower arm 2 b do not become an obstacle to the insertion of the insert 1. Therefore, the insert 1 can be fixed relative to the cylinder block 10, maintaining the mounting feature (insertion feature) of the insert 1 good.

[0061] In the second embodiment of the present invention, the insert 1 is fixed relative to the cylinder block 10 so as not to be moved in the flow direction of the cooling water, by inserting a wedge 16 into a clearance between the insert 1 and the water hole portion 10 b as illustrated in FIG. 2A, or by poring and solidifying a rubber 17 into a clearance between the insert I and the water hole portion 10 b as illustrated in FIG. 2B. The insert 1 may not be supported or may be supported at the lower end of the insert. If not supported at the lower end, the support of the insert becomes a cantilever support at the upper end. The wedge 16 or the rubber 17 is part of the fixing and supporting structure 30 of the second embodiment of the present invention.

[0062] With an effect of the second embodiment of the present invention, since the wedge 16 is inserted or the rubber 17 is pored after the insert I has been inserted into the water jacket 11, the wedge 16 and the rubber 17 do not become an obstacle to the insertion of the insert 1. Therefore, the insert 1 can be fixed relative to the cylinder block 10, maintaining the mounting feature (insertion feature) of the insert 1 good.

[0063] In the third embodiment of the present invention, as illustrated in FIGS. 3A and 3B, a clip engagement hole is formed in the insert 1 and the water hole portion 10 b around the water hole 12, and legs of a clip 18 are inserted into the clip engagement hole of the insert 1 and the clip engagement hole of the water hole portion 10 b, whereby the insert 1 is fixed relative to the cylinder block 10 so as not to be moved in the flow direction of the cooling water. The clip 18 extends over the insert 1 and the water hole portion 10 b. The insert 1 is fixed relative to the cylinder block 10 at the water hole portion 10 b. The insert 1 may be or may not be supported at the lower portion of the insert. If not supported at the lower portion, the support becomes a cantilever support at the upper end of the insert. The clip 18 is the fixing and supporting structure 30 of the third embodiment of the present invention.

[0064] With an effect of the third embodiment of the present invention, since the insert 1 is fixed by the clip 18 after the insert 1 has been inserted into the water jacket 11, the clip 18 does not become an obstacle to the insertion of the insert 1. Therefore, the insert 1 can be fixed relative to the cylinder block 10, maintaining the mounting feature (insertion feature) of the insert 1 good.

[0065] In the fourth embodiment of the present invention, as illustrated in FIGS. 4A and 4B, a groove 19 is formed in the water hole portion 10 b around the water hole 12, and a key 20 fitted into the groove 19 is formed in the insert 1. The key 20 is fitted into the groove 19 after the insert I has been inserted into the water jacket 11, whereby the insert 1 is fixed relative to the cylinder block 10 so as not to be moved in the flow direction of the cooling water. The insert 1 is fixed relative to the cylinder block 10 at the water hole portion 10 b. The insert 1 may be or may not be supported at the lower portion of the insert. If not supported at the lower portion, the support becomes a cantilever support at the upper end of the insert. The key 20 and the groove 19 are the fixing and supporting structure 30 of the fourth embodiment of the present invention.

[0066] With an effect of the fourth embodiment of the present invention, since the insert 1 is fixed by the key 20 and groove 19 after the insert 1 has been inserted into the water jacket 11, the key 20 and groove 19 do not become an obstacle to the insertion of the insert 1. Therefore, the insert 1 can be fixed relative to the cylinder block 10, maintaining the mounting feature (insertion feature) of the insert 1 good.

[0067] In the fifth embodiment of the present invention, as illustrated in FIGS. 5A, 5B and 5C, the cylinder block 10 has a water jacket wall surrounding the water jacket 11, and a stopper (as the fixing and supporting structure 30) for preventing the insert 1 from moving downstream in a flow direction of the cooling water is formed to the water jacket wall.

[0068] The stopper is a protrusion 21 formed in at least one of a bottom wall portion and an outer side wall portion of the water jacket wall. In FIGS. 5A and 5B, the protrusion 21 is formed in the bottom surface of the water jacket 11. In FIG. 5C, the protrusion 21 is formed in the outer side surface of the water jacket 11. In the insert 1, at a portion corresponding to the protrusion 21, a concave groove 22 is formed. The protrusion 21 enters and engages the groove 22. The protrusion 21 is the stopper (as the fixing and supporting structure 30) of the fifth embodiment of the present invention.

[0069] With an effect of the fifth embodiment of the present invention, since the protrusion 21 enters and engages the groove 22, the insert 1 is not dislocated from the normal position when the insert 1 receives a flow pressure from the cooling water. Since the protrusion 21 is formed at the bottom surface or the outer side surface of the water jacket 11, the protrusion 21 does not become an obstacle to the insertion of the insert 1. Therefore, the insert 1 can be fixed relative to the cylinder block 10, maintaining the mounting feature (insertion feature) of the insert 1 good.

[0070] In the sixth embodiment of the present invention, as illustrated in FIG. 6, the stopper (as the fixing and supporting structure 30) is an extension 24 extending from a cylinder head 23 mounted to the cylinder block 10 into the water jacket 11. The extension 24 supports the insert 1 from the downstream side of the insert 1 and prevents the insert 1 from being dislocated in the flow direction of the cooling water. The extension 24 may support and fix the upper portion of the insert 1 in a thickness direction of the insert as illustrated in FIG. 6. The extension 24 may be a member separately manufactured from the cylinder head 23 and coupled to the cylinder head, and may support and fix the upper portion of the insert 1 when the cylinder head 23 is mounted to the cylinder block 10.

[0071] With an effect of the sixth embodiment of the present invention, since the extension 24 supports the insert 1 from the downstream side of the insert 1, the insert 1 is prevented from being dislocated from the normal position in the flow direction of the cooling water when the insert 1 receives a flow pressure from the cooling water. Since the cylinder head 23 is mounted onto the cylinder block 10 after the insert 1 has been inserted into the water jacket 11, the extension 24 does not become an obstacle to the insertion of the insert 1. Therefore, the insert 1 can be fixed relative to the cylinder block 10, maintaining the mounting feature (insertion feature) of the insert 1 good.

[0072] In the seventh embodiment of the present invention, as illustrated in FIGS. 7A and 7B, the stopper (as the fixing and supporting structure 30) is an extension 26 extending from a cylinder head gasket 25 mounted to the cylinder block 10 into the water jacket 11. The extension 26 supports the insert 1 from the downstream side of the insert 1 and prevents insert 1 from being dislocated in the flow direction of the cooling water.

[0073] With an effect of the seventh embodiment of the present invention, since the extension 26 supports the insert 1 from the downstream side of the insert 1, the insert 1 is prevented from being dislocated from the normal position in the flow direction of the cooling water when the insert 1 receives a flow pressure from the cooling water. Since the cylinder head gasket 25 is mounted onto the cylinder block 10 after the insert 1 has been inserted into the water jacket 11, the extension 26 does not become an obstacle to the insertion of the insert 1. Therefore, the insert 1 can be fixed relative to the cylinder block 10, maintaining the mounting feature (insertion feature) of the insert 1 good.

[0074] In the eighth embodiment of the present invention, as illustrated in FIGS. 8A, 8B and 8C, the stopper (as the fixing and supporting structure 30) is a protrusion 

I claim:
 1. A method of determining air humidity with a capacitive moisture measuring element, comprising: a method step in which a current moisture signal is ascertained from electrical properties of the moisture measuring element, and a method step in which a corrected moisture signal is calculated from the current moisture signal, wherein in a measuring phase with rising relative air humidity RH the corrected moisture signal is the current moisture signal increased by a correction valure a(RH) and wherein in a measuring phase with falling relative air humidity RH the corrected moisture signal is the current moisture signal reduced by a correction value a(RH).
 2. A method as set forth in claim 1, wherein the correction value a(RH) is constant.
 3. A method as set forth in claim 1, wherein the correction value a(RH) is used from a stored table or is calculated as a mathematical function.
 4. A method as set forth in claim 1, wherein charging and/or discharging the capacitive moisture measuring element by way of a first measuring resistor provides for ascertaining a first time constant or a first period duration of the charging and/or discharging operation, and charging and/or discharging the moisture measuring element by way of a second measuring resistor, whose value is different from the value of the first measuring resistor, provides for ascertaining a second time constant or a second period duration of the charging and/or discharging operation.
 5. A method as set forth in claim 4, wherein the capacitance of the moisture measuring element is calculated from the two time constants or the two period durations, and the moisture measuring element for the calculation operation is modelled by a parallel circuit of an ideal capacitor and an ohmic resistance.
 6. A method as set forth in claim 4, wherein the ohmic resistance value of the moisture measuring element is calculated from the two time constants or the two period durations, and the moisture measuring element for the calculation operation is modelled by a parallel circuit of an ideal capacitor and an ohmic resistance.
 7. A method as set forth in claim 1, wherein the current moisture signal is ascertained with the capacitance of the moisture measuring element.
 8. A moisture sensor comprising a capacitive moisture measuring element and a correction unit with means for carrying out the method as set forth in claim
 1. 9. A moisture sensor as set forth in claim 8, further comprising a signal processing unit connected to the moisture measuring element with means for carrying out the method as set forth in claim
 4. 10. A moisture sensor as set forth in claim 8, further comprising a monitoring unit by which a certain deviation in an ohmic resistance value of the moisture measuring element over a relatively long period of time can be detected and signalled. 